Field
The present disclosure relates generally to communication systems, and more particularly, to methods and apparatus for efficient transport and management of a positioning and timing almanac at mobile stations supported by a positioning assistance server.
Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communications with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA), 3GPP Long Term Evolution (LTE) systems, and orthogonal frequency division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communication system may simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link may be established via a single-in-single-out, multiple-in-single-out or a multiple-in-multiple-out (MIMO) system. The method and apparatus described herein may be used with a conventional wireless system or with a MIMO system.
A MIMO system employs multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas may be decomposed into NS independent channels, where NS—≧min {NT, NR}. Each of the NS independent channels corresponds to a dimension. The MIMO system may provide improved performance (e.g., higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.
A MIMO system may support time division duplex (TDD) and/or frequency division duplex (FDD) systems. In a TDD system, the forward and reverse link transmissions are on the same frequency region so that the reciprocity principle allows the estimation of the forward link channel from the reverse link channel. This enables the base station to extract transmit beamforming gain on the forward link when the multiple antennas are available at the base station. In an FDD system, forward and reverse link transmissions are on different frequency regions.
As mobile stations have become more capable with more features provided use and reliance on those features has grown. One such feature is position location, commonly known as global positioning systems (GPS). Most users are familiar with GPS systems and have used them for locating points of interest or for obtaining directions. Terrestrial radio resources (e.g., cellular base stations, TV broadcasting, FM/AM radio signals and WiFi access points) are more widely used for positioning now because of increased availability for mobile stations. In order to take advantage of these communication receivers for positioning, additional information must be delivered to a mobile station for use with mobile based positioning.
The information package, often known as an almanac, grows quickly in size as it covers larger areas of transceivers with descriptions of their location, coverage, and clock calibration data. It is important to deliver the almanac efficiently with minimum cost. There is a need in the art for efficient almanac delivery and maintenance to reduce unnecessary transmissions between mobile stations and the server.